Is it incumbent upon my mother to repeat the 'Umrah after she performed it while menstruating, knowing that her menstruation began an hour before her travel, after an interruption that lasted for more than a year?

If menstruation ceases due to illness or breastfeeding and then returns, it is considered menstruation. And if it ceases due to old age (after fifty) and then returns, the correct view is that it is menstruation as long as the blood possesses its characteristics, because menopause is not limited by a specific time. So, if the blood that your mother experienced was menstrual blood, then her 'Umrah was not complete; because a menstruating woman is forbidden from performing Tawaf until she purifies herself. She must repeat the Tawaf, Sa'i, and Taqsir, while avoiding the prohibitions of Ihram. However, if the blood did not possess the characteristics of menstruation, then it is a hemorrhage, and her 'Umrah is not invalid.